Electric-furnace control



April 28, 1925. 1,535,883

I H. A. WINNE ELECTRIG FURNACE CONTROL Filed Nov. 25, 1921 Invehtor:Harry A.Winhe His Attorneg.

Patented Apr. 28, 19 25.

UNITED STATES PATENT OFFICE.

HARRY A. WINNE, OF SCHENECTADY, NEW YORK, ASSIGNOR'TO GENERAL ELECTBIC pCOMPANY, A COBPORATION OF NEW YORK. y 4 V Enorme-ruana@ CONTROL.

Application filed November 23, 1921. Serial No. 517,401.

To all whom it 'may concern:

Be it known that I', HARRYVA. WINNE, a citizen of the United States,residing at Schenectady, in the county of Schenectady, State of'Ne'wYork, have invented certain new and useful Improvements in Electric-Furnace Controls, of, which the following is a specification.

My invention relates to the control of electricfurnaces and has for itsobject the provision of means whereby an improved reguw lation of thefurnace current is obtained in a simple and eflicent'manner.

My invention relates more specifically t'o the control of an electricare furnace in.

controllng the electric motor which operates` the electrode. With thisarrangement there is under some conditions possibility of a huntingaction of the moving member of p the contact making ammeter due to lagin some of the circuit controlling parts and also due in part tomomentum in themotor arma ture and electrodes moved thereby. One of theobjects of my invention is to overcome this tendency. p

In carrying-out my invention I provide means whereby the moving'memberof the controlling means, such as the contact making ammeter, issupplied with a positive force tending to return it to neutral positionas soon as it makes a contact which starts the motor for shifting theelectrodes. This causes themember to be pulled away from the stationarycontact earlier in the operating cycle than would ordinarily be thecase. The result is that a closer regulation of the current is obtained.without the objcctionable hunting action of the mo'vable member. Otherobjects andpurposes of my inj vention will appear in the course of thefollowing specification in which I have shown ny invention embo'died inconcrete form for purposes of illustration. I

Referring to the accompany'ing drawing i in which I have shown the partsmore or less which has a screw threade'd relation with a. screw 10connected with the electrode' whereby the electrode will be moved up anddown very slowly through this speed red1icing gear. The field of themotor F is suppled from the direct current mains 11 and 12, there beinga resistanc'e R in' the field circuit controlled by a cont actor' 13 forvarying the speed of the moton...- Reversing switches 14: and 15 areprovided for reversing the motor armature current which is supplied fromthe mains 11 and 12 "an'd adynamc brake resistance 16 controlled by acontactoi' 17 conncle across khe motor temnas is provi e or uic sto t emotor after the power i s cut ta. lb canical interlocks 18 and 19cooperate with an extension 20 on the moving element of the contactor 17for preventing the closing of one of the reversing contactors until thecontactor 17, which controls the dynamic braking circuit, opens due tothe substantial stopping of the motor. The two reversing ing ammeterhaving an Operating coil 21 connectedto-a current transformer 22 in 'thesupply conductor 8, a resistance 23 be- ,control to manual control andvice versa.

contactors are controlled by a contact makt When the switch 31 is inposition to bridge whereas when it is moved over so as to enu gage thecontact 33, the control will be manual through the push buttons 34 and35.

As thus far described it will be seen that assuming that the switch 31is in engagement with the contaets 32 the control of the electrode 5will be automatically effected in accordance with the variations in 'thecurrent 'of the sup ply conductor 8. If,

for inst'ance, current 'in the conductor 8 becomes too high thecontactmaking ammeter will operate to make contact at 27 and energizethe reversing contactor 14 whereby the electrode will be raised toreduce the current. On the other hand, if the current in the conductor 8becomes too low the con-g tact is made at 26 so as to energize thecontactor 15 and close the motor circuit in a direction to lower theelectrode; Each time one of the reversing contactors opens 'to open themotor armature circuit the con tactor 17 wilL'close ,toestablish adynamic braking circuit through the resistance 16 and the otherreversing contactor cannot close until the contactor 17 'is opened bythe slowing d'own of the motor substantially to rest. When the switch 31is 'in the auto natic position; namely, in engagement with the contacts32, the contactor 13 Will close so as to short circuit the resistance Rand reduce the speed of the motor. When the switch 31 is moved intoengagenent with the contact 33 the control of the reversing' contactorswill be through the push buttons' 34 and 35. In this position, however,the conta'ctor 13 will be open and the resistance R will be in serieswith the field so as to speed up the motor. There will therefore be a'higher speed of the motor during manual v which is energized to movethe member in either direction depending upon which of the contacts 26or 27 isengaged. This winding 36 is energized across the directcurrentsupply circuit 11, 12`either through resistances 7' or 7-' andone of the reversingcontactors 14, 15. 'Whencontactor 14 closes due tothe engagement'of the arm 24 with the contact 27, a. circuit iscompleted through the winding 36 from the supply line 11 throughthe'resistance-r, winding 36, and the upper switch arm of contactor 14to line 12. The energization of winding 36 is now in a direction toforce the. arm.24 upward out of engagementwith the contact 27. If

the` contactor 15 is closed due to the closing' of the circuit atcontact 26, the circuit will then be from th -supply line 11 through theupper switch arm of con'tactor 15 through clear.

winding 36 and to`-supply line 12 through resistance r'. The currentthrough the winding 36 is'now reversed so ;that the force'` upon the arm24 is in the downward direc tion tending to break the contact at-26. A

dash pot 37 retards the action ofthe wind ing '36 upon its moving core.It will therefore be seen that whenever the contact is made at either 26or 27 a force is-set up tending to move the arm back to the centralposition. The 'result of this is more positve action of the contactmaking anj meter resulting in a closer calibration with no tendency ofthe member to hunt. A numerical example will make .this point Assumingthat the member 24 balances. in a neutral positionwith' a current of oneampere in the coil 21 'and that a decrease of current .to .95 amperewill cause the electrode 5. .At the same time the-coil 36' willbeenergized in a direction tendi'g to lift the arm 24 out of engagementwith the contact 27. If the 'force due to the wind*- ing 36 were notpresent, 'the arm'24 would not tend to separate from contact 27 untilthe current in the contact making ammeter had actually been reduced to1.05 amperes and the lag of the mechanism and the over:

travel of the electrode might cause the -current to drop to .95 amperebefore the electrode motion actually ceased. The -force set up by thewinding 36 may be such that the member 24 will tend to separate' from'the contact 27 when the current in the winding 22 has been reduced toonly- 1.1 amperes. consequently, assuming the sa'me'lag and *overtravelin the mechanism, at the tim the electrode motion' is actually stopped,the current in the coil 22 will have been reduced only to the normal-value of one ampere. In other words, by the provision of-. myarrangement the natural tendency for an overtravel which would result inthe continuous vibration or hunting action of the mem-' ber 24 will beto a very large extent overcome While I have described my invention as iembodied in concrete form and as operat ing in a specific manner inaccordance with the provisions of the patent statutes, it should beunderstood that I do not limit my invention thereto, since variousmodifica tions thereof will suggest themselves to those skilled in theart without departing from the spirit of my invention, the scope ofwhich is set forth in the annexed'claims.

' What I claim 'as new and desire' to se- V electrode cure by LettersPatent of the United States,

1'. A regulating system for e-lectric. furnaces comprising incombination with an 2 an energy supply source therefor, an electrc motorfor' moving said electrode, electromagnetic means res nsive tovariations in the electrode circut for controlling the. movement of'said electrode by said motor in two-directions, a. pair of resistancedevices connected in series across said supply source, a secondelectromagnet mechanically connected* to the first, and' electricalconnections between one terminal of said secv ond electromagnet and oneterminal of said motor and between the other terminal of said secondelectromagnet and a point between said resistance devices, whereby saidsecond electromagnet is energized to oppose the first upon movement ofsaid electrode in either direction.

2. A regulating system for electric furnaces comprsing in combinationwith an electrode, an energy supply source therefor,

an electric motor operatively connected to adjust said electrode,"reversing switches for said motor, a contact making ammeter forcontrolling the reversing switches having a winding in the electrodesupply circuit and an element movable by said winding to oppositecontact making positions from an intermediate position in accordancewith variations in the electrode circuit, a pair of resistancesconnected in series across said supply source, an electromagnet, anOperating connection between said electromagnet and said element, andelectrical connections between one terminal of said electromagnet andone terminal of said motor and between the other terminal of saidelectromagnet and a point between said resistances' whereby saidelectrona-gnet is energized through said reversing switches concurrentlywith said motor to exert a force tending to return said element to itsintermediate position.

In witness whereof, I have hereunto set my hand this 22nd day ofNovember, 1921.

HARRY' A. WINNE.

